Depending on the different principle of optical switches, there are multiple ways of optical switch to be realized, such as traditional mechanical optical switches, micro-mechanical optical switches, thermal optical switches, liquid crystal optical switches, electro-optical switch and acousto-optical switch. Where traditional mechanical optical switches, micro-mechanical optical switches and thermal optical switches, because of their characteristics are widely used in different occasions.
Currently the most widely used is still the traditional 1X2 and 2X2 Mechanical Optical Switch. The traditional mechanical optical switch could move through fiber optic light directly coupled to the output terminal, then use the prisms and reflector mirrors to switching the optical path, and send the optic light directly or reflect to the output terminal.
There are mainly three types of mechanical optical switch: one is the prism optical switching technology, the second is the mirror switching technology, the third is to switch the optical path by moving the optical fiber.
The prism type optical switch operating principle - Fiber and lens (collimator) which play the role of collimated is connected, then make them fixed, and change the optical path between input and output ports by moving prism.
The reflector type optical switch operating principle - when the reflector does not enter the optical path, the optical switch is in the through state. When the reflector in the intersection of two optical path position, the optical switch is in the cross state.
The moving the optical fiber type optical switch operating principle - Fix one end of the optical fiber, moving the other end of the optical fiber and coupled with fixed fiber of different port, and make the optical path switching. Such optical switch has low return loss, and affected by the environment temperature is big, so it is not a real sense of the commercial products. In China, the domestic commercial optical switch are mainly prism type optical switch and reflector type optical switch.
The advantages of mechanical type optical switch is low insertion loss (<1dB) and high isolation (> 45dB) is independent of wavelength and polarization, the production technology is mature. The disadvantage is that the switching time is a little long (ms of magnitude), the volume is too large, and difficult to make large-scale optical switch matrix, and sometimes there is rebound jitter and poor reproducibility problems.
Mechanical type optical switch has been widely used in recent years, but with the growing size of the optical network, such a switch is difficult to meet the needs of future high-speed and high-capacity optical transport network development demand.